masterdrive motor sharp sound

we have a third-party motor connected to the below Siemens masterdrive.
when we run it with V/Hz open loop frequency control P100 = 0 , the motor gives a sharp acute sound .
but if we do this with Frequency control without speed actual value encoder P100 = 3 , the motor is quiet and runs smoothly .
why is this big difference between the two operation modes ?
what causes the sharp sound with v/hz ?

6SE7037-0EK60
simovert masterdrives vector control converter chassis unit, ip00 3 380-480v ac, 50/60hz, 690 a nom. power ratings: 400kw

The Zero setting in P100 means the drive is looking for a tachometer feedback even though it is in V/Hz control. Setting P100 to 3 removes the need for the external feedback loop, it is in Sensorless Vector Control for velocity only. In order to use any type of Vector Control, you must use one of the pre-defined Siemens motors (which you did not do), or preform an auto tuning procedure to make the drive match the motor. Presumably someone did that, which is why the motor runs better when in setting 3.

The manual warns you that on motors over 200kW, you should not use any of the open loop V/Hz settings (0, 1 or 2), likely because the motor electromagnetic equivalency circuit is incompatible with the way they fire the transistors in this drive unless the tuning has been performed. When you choose drives that are very powerful in terms of performance, you give up some of that ability to be "simple" and run any motor without tuning it, the concepts are essentially mutually exclusive. The thought process is that if you did not want the high performance, you would have paid a LOT less for the simpler drive. You have one of those high performance drives.

After checking the parameters, we found that we tried the motor at p100=1 (not 0).
Anyway it is clear now why the whistling is happening, thank you for your help.